remove dead unpremul checks

src/effects/SkArithmeticMode_gpu.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkArithmeticMode_gpu.h"
 
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "GrFragmentProcessor.h"
 #include "GrInvariantOutput.h"
 #include "GrProcessor.h"
 #include "GrTexture.h"
 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLProgramDataManager.h"
 #include "glsl/GrGLSLUniformHandler.h"
 #include "glsl/GrGLSLXferProcessor.h"
 
-static const bool gUseUnpremul = false;
-
 static void add_arithmetic_code(GrGLSLFragmentBuilder* fragBuilder,
                                 const char* srcColor,
                                 const char* dstColor,
                                 const char* outputColor,
                                 const char* kUni,
                                 bool enforcePMColor) {
     // We don't try to optimize for this case at all
     if (nullptr == srcColor) {
         fragBuilder->codeAppend("const vec4 src = vec4(1);");
     } else {
         fragBuilder->codeAppendf("vec4 src = %s;", srcColor);
-        if (gUseUnpremul) {
-            fragBuilder->codeAppend("src.rgb = clamp(src.rgb / src.a, 0.0, 1.0);");
-        }
     }
 
     fragBuilder->codeAppendf("vec4 dst = %s;", dstColor);
-    if (gUseUnpremul) {
-        fragBuilder->codeAppend("dst.rgb = clamp(dst.rgb / dst.a, 0.0, 1.0);");
-    }
-
     fragBuilder->codeAppendf("%s = %s.x * src * dst + %s.y * src + %s.z * dst + %s.w;",
                              outputColor, kUni, kUni, kUni, kUni);
     fragBuilder->codeAppendf("%s = clamp(%s, 0.0, 1.0);\n", outputColor, outputColor);
-    if (gUseUnpremul) {
-        fragBuilder->codeAppendf("%s.rgb *= %s.a;", outputColor, outputColor);
-    } else if (enforcePMColor) {
+    if (enforcePMColor) {
         fragBuilder->codeAppendf("%s.rgb = min(%s.rgb, %s.a);",
                                  outputColor, outputColor, outputColor);
     }
 }
 
 class GLArithmeticFP : public GrGLSLFragmentProcessor {
 public:
     void emitCode(EmitArgs& args) override {
         const GrArithmeticFP& arith = args.fFp.cast<GrArithmeticFP>();
 
@@ skipping 237 matching lines @@
     float k1 = d->fRandom->nextF();
     float k2 = d->fRandom->nextF();
     float k3 = d->fRandom->nextF();
     float k4 = d->fRandom->nextF();
     bool enforcePMColor = d->fRandom->nextBool();
 
     return GrArithmeticXPFactory::Create(k1, k2, k3, k4, enforcePMColor);
 }
 
 #endif